1. Field of the Invention
The present invention relates to a phase-change memory device, and more particularly, to the memory cell structure of the phase-change memory device.
2. Description of the Related Art
Phase-change memory devices have recently been developed as new-type nonvolatile memories.
Phase-change memory devices employ, in memory elements, a phase-change film formed of a chalcogenide compound, as used in, for example, CD-RWs and DVD-RAMs. Depending upon whether the phase-change film is in the amorphous or crystalline state, “0” or “1” is stored. Phase-change memory devices are characterized not only in that they are nonvolatile, but also in that they allow data to be written more quickly and to be rewritten a much larger number of times than do existing flash memories.
For example, “Non-Volatile High-Density, High-Performance Phase-Change Memory” by Scott Tyson et al. in IEEE Aerospace Conference 2000 describes the memory structure of a conventional phase-change memory device (see, for example, pages 385 to 390). In the disclosed structure, since a phase change occurs only in part of a chalcogenide compound, the voltage applied to the compound can be reduced, thereby reducing the power consumption of the phase-change memory device. However, this device requires a large memory cell array area. Further, if one end of each of the memory cells formed of the chalcogenide compound is connected to one end of any other memory cell by, for example, a metal wire, the power consumption of the phase-change memory device is increased.